1. Field
The following description relates to a size sorting device for carbon nanotube agglomerate, and a method for separating and collecting dispersed carbon nanotubes using the same.
2. Description of Related Art
A carbon nanotube (CNT) is a material composed of carbon atoms bonded to each other in hexagonal honeycomb patterns, forming a tube shape as a whole. Additionally, carbon nanotubes feature high anisotropy and have various structures such as single-walled structures, multi-walled structures, bundle structures, etc. Carbon nanotubes include nanomaterials having a diameter on a nanometer scale (1 nm=one billionth of 1 m), and generally have extraordinary mechanical and electrical properties, excellent field emission properties, high efficiency properties like hydrogen storage mediums, among other unique properties.
Carbon nanotubes may be synthesized by various methods such as electric discharge, thermal decomposition, laser deposition, plasma chemical vapor deposition, thermochemical vapor deposition, and electrolysis. Since most carbon nanotubes exist in bundle forms in the stage of synthesis, it is important to separate and disperse the carbon nanotubes one by one in order to utilize the excellent mechanical and electrical properties of the carbon nanotubes.
Typically, as a way to disperse carbon nanotubes in a liquid, a physical dispersion method such as an ultrasonic process is used. Such a physical dispersion method using an ultrasonic process may include a method of putting a single-walled carbon nanotube agglomerate in acetone and dispersing the carbon nanotubes in the acetone using the ultrasonic process. In addition to performing the ultrasonic process, the method includes improving hydrophilic properties of carbon nanotubes by adding a material such as a surfactant to the solvent. For example, Korean Patent Laid-open Publication No. 2010-0051927 describes a combined pulverization and dispersion system enabling dispersion of carbon nanotubes. These carbon nanotube dispersion methods, however, may not only lack dispersion effects but may also cause damage to the carbon nanotubes.
Further, conventional techniques of collecting and separating certain nanotubes by using a magnetic field are not aimed at collecting carbon nanotubes dispersed from carbon nanotube agglomerates, but are mainly intended to separate carbon nanotubes free of metal impurities by using a magnetic field or to selectively separate only semiconducting or metallic carbon nanotubes that react to a magnetic field.
In order to manufacture a carbon nanotube complex with vast market potential, it is required to acquire excellent physical properties or electrical conductivity with a minimum use of carbon material. Accordingly, it is important to obtain a high degree of dispersion of carbon materials. As an example, if ITO (Indium Tin Oxide), most of which is imported, can be replaced with a carbon nanotube polymer film, it may be possible to obtain an import-substituting effect amounting to about  1.3 trillion for 5 years. Moreover, such high efficiency carbon nanotube dispersion techniques may find applications to various fields such as conductive polymer, conductive e-paint, electromagnetic field absorber, and products such as a tennis rackets or a racing bicycles, etc., thus producing higher added value.